---
title: "Type Conversion"
id: typeconv
pg_version: "20devel"
---

<a id="typeconv"></a>

# Type Conversion

## Table of Contents

- [10.1. Overview](typeconv-overview.md)
- [10.2. Operators](typeconv-oper.md)
- [10.3. Functions](typeconv-func.md)
- [10.4. Value Storage](typeconv-query.md)
- [10.5. `UNION`, `CASE`, and Related Constructs](typeconv-union-case.md)
- [10.6. `SELECT` Output Columns](typeconv-select.md)

SQL statements can, intentionally or not, require the mixing of different data types in the same expression. PostgreSQL has extensive facilities for evaluating mixed-type expressions. 

In many cases a user does not need to understand the details of the type conversion mechanism. However, implicit conversions done by PostgreSQL can affect the results of a query. When necessary, these results can be tailored by using *explicit* type conversion. 

This chapter introduces the PostgreSQL type conversion mechanisms and conventions. Refer to the relevant sections in [Chapter 8](datatype.md) and [Chapter 9](functions.md) for more information on specific data types and allowed functions and operators.